@Boek 

The roaming is controlled by the phone itself. On a mesh network like our Deco units, they use the roaming protocols 802.11 k/v/r which tells the client device where to do or what to connect to and help with seamless connection from one AP to another. In your case the router and the AP do not work in conjunction but are literally two wireless networks with the same network name.

What you may need to do is see if there is a way to modify threshold to have the client device choose another network based on signal strength or have something on the phone decide what to connect to.

@Tony  Thanks so much for the reply.  Would it help if I replaced my unifi access point with a TP-Link unit like the TP-Link Omada AC1350?

@Boek 

I think you might still be in the same situation. In going back to your original issue, have you tried naming both networks differently? Do they both show at the same time? I think what may be happening is when you look at your available Wi-Fi networks your Android is consolidating both networks to one name.

@Tony I have tried naming the SSIDs separately.  When I do that, both networks show up and work well, though I obviously can't roam between them and must instead manually switch networks on my android or computer.  All my client devices are having the same issue. 

This is me standing under the tplink.

This is me under the unifi

@Boek 

Ok so making the names the same gives you one network, but not the mesh roaming you are looking for. What you want is an actual mesh router that will give you the one network and seamless roaming. Now you mentioned you just got the AC1750, is that the Archer A7?

If so, you can possibly get a OneMesh network going which will need an extender that supports OneMesh: link

OneMesh is aimed at giving someone an option to get mesh capabilities without needing to purchase a whole mesh network.

Here is a link that talks about it if you wanted to know more: link

@Tony It is the Archer A7. I see that it is designed for a mesh network.  Do you think that is part of the problem because I have a secondary AP plugged in through an ethernet cable? I already have the 2nd AP and the ethernet cable run so I don't want to lose that.  Should I try a different router that isn't designed for mesh networks? 

@Boek 

The A7 is a regular Wi-Fi router, a Deco is designed for a mesh network. In your case you are just using a router and an AP unit with the same network names. The A7 also happens to have the firmware to set it up with one of our extenders to create an OneMesh network.

@Tony Great to know.  Thanks!